Originally Posted by CZ550
"Remember to add at least 72 fps to correct the 20"-barrel velocity to 24"-barrel length". I typically add 100 fps as an average. Not that I've had a 20" .458 WM, but largely based on experiences of two distinct Marlins in .45-70:several in 22" and one in the 18.5" GG. When pushed to the limit (probably over 40,000 psi), but safe in my rifles, the 22" would give ~2120 fps from the 405 Rem, and the 18.5" barely made it over the ~2000 fps mark. A loss of about 100 fps from a 3.5" shorter barrel.

www.bigbores.ca

Sir Bob,
I do not doubt your finding.
Below 20" barrel length, a lot more is lost per inch subtracted.
Above 24" barrel length, a lot less is gained per inch added.
Bullet weight versus powder burn rate is mostly a wash.

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Ron aka "Rip" for Riflecrank Internationale Permanente
NRA Life Benefactor and Beneficiary
.458 Winchester Magnum, Magnanimous in Victory
THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.